The invention relates to a method and a device for the production of a solid-forming or foam-forming flowable reaction mixture from at least two flowable components reacting with each other, which are fed continuously to a mixing zone and mixed together, wherein, the volumetric rate of flow of at least one component is measured and its density is determined.
It is known from German Auslegeschrift No. 2,543,302 to make the gas charge (i.e. the amount of dissolved gas in the component) of the components reproducible and measurable and, in addition, to control the gas charge automatically. For this purpose, the volume of the gas-charged reactant which is delivered per unit time is measured at a first pressure level which is kept higher or lower than a subsequent second pressure level. The reactant is then brought to a second pressure level which is kept lower or higher than the first pressure level. The volume delivered per unit time is measured again. The difference is determined as a gauge of the gas charge and this value is compared with a predetermined set value. The quantity of gas to be added is then controlled manually or by means of an automatic control device so as to maintain the set value. The production costs are high with this arrangement. Additionally, in many instances, a constant quantitative rate of flow is needed.
A method and an apparatus are known from German Offenlegungsschrift No. 2,724,132, whereby the quantitative rate of flow can be determined so that the stoichiometric metering ratio can again be adapted to the predetermined set value in the event of deviations on the basis of the measurement. For this purpose, it is necessary to use expensive apparatus in which a subsidiary stream is divided off. The quantity of material by volume which has passed through this subsidiary stream during a predetermined time interval is determined using a complicated weighing device. The density of the component is determined from this measurement as a quotient of the quantity by weight and the quantity by volume. The volumetric rate of flow is measured, from which the quantitative rate of flow of the main stream is finally determined as a product of the density of the component and the volumetric rate of flow of the main stream. The gas content of the component is not however considered during the subsequent control of the metering ratio based on quantitative rate of flow determined.
It is theoretically possible to combine the two methods and devices described above in order to achieve an end product of the desired quality. This combination would be so expensive, however, that it is unacceptable in practice.
The object of the invention is to provide a method and a device which allows both the stoichiometric metering ratio of the components and the gas content thereof to be easily controlled.